1. Field of the Invention
This invention relates to a method of and a service node for providing services in an intelligent communications network.
2. Related Art
Before the advent of the stored program controlled (SPC) exchange, the Public Switched Telephone Network (PSTN) comprised electromechanical exchanges, such as Strowger and Crossbar exchanges, and electronic exchanges, such as TXE2 and TXE4 exchanges. However, even the most advanced of these types was only capable of performing a limited number of functions over and above merely switching a call, i.e. making a connection between an incoming channel or line and an outgoing channel. Furthermore, such additional functions were limited to operations for improving the performance of the network, for example, a repeat attempt at reaching a destination number via an alternative outgoing route in the event that the first-choice route is busy.
SPC exchanges enabled customers to control various supplementary services via signals entered on their telephone keypad using the * and # buttons. However, the introduction of a new service, or the modification of an existing service, meant that the control program had to be updated in each of the SPC exchanges.
The current concept of an intelligent communications network is based on a core of interconnected Main Digital Switching Units (MDSU's), with local exchanges connected to the MDSU's (usually with each local exchange connected to two MDSU's for network resilience in the event of an MDSU failure), and with services being provided and controlled by discrete service nodes at various positions in the network.
Each service node is connected to an MDSU of the network, which recognizes service access digits dialled by a customer and routes the call to the service node for the provision of the requested service for the customer.